Securing element for resheathing an intravascular device and associated systems and methods

ABSTRACT

Devices and methods for securing a cover of a retrieval device while the retrieval device is resheathed to a more proximal position within a delivery sheath are disclosed herein. A retrieval device may include, for example, a securing element configured to grip the cover when the retrieval device is pulled proximally, to thereby secure the cover. A method of positioning the retrieval device may include, for example: (a) advancing the retrieval device distally through a delivery sheath to a partially deployed state while the securing element is in a first state, and (b) retracting the clot retrieval proximally from the partially deployed state while the securing element is in a second state that grips the cover to secure the cover.

CROSS-REFERENCE TO RELATED APPLICATION(S)

The present application is a divisional of U.S. patent application Ser.No. 15/629,786 filed Jun. 22, 2017, which is incorporated herein byreference in its entirety.

TECHNICAL FIELD

The present technology relates generally to devices and methods forsecuring a cover of a retrieval device while the retrieval device isresheathed to a more proximal position within a delivery sheath.

BACKGROUND

Many medical procedures use medical device(s) to remove an obstruction(such as clot material) from a body lumen, vessel, or other organ. Aninherent risk in such procedures is that mobilizing or otherwisedisturbing the obstruction can potentially create further harm if theobstruction or a fragment thereof dislodges from the retrieval device.If all or a portion of the obstruction breaks free from the device andflows downstream, it is highly likely that the free material will becometrapped in smaller and more tortuous anatomy. In many cases, thephysician will no longer be able to use the same retrieval device toagain remove the obstruction because the device may be too large and/orimmobile to move the device to the site of the new obstruction.

Even in successful procedures, a physician must be cautious to preventthe walls of the vessel or body lumen from imparting undesired forces toshear or dislodge the obstruction as it passes through the vasculatureduring removal. These forces have the potential of fragmenting theobstruction. In some cases, the obstruction can simply break free fromthe retrieval device and can lodge in a new area causing more concernthan the original blockage.

Procedures for treating ischemic stroke by restoring flow within thecerebral vasculature are subject to the above concerns. The brain relieson its arteries and veins to supply oxygenated blood from the heart andlungs and to remove carbon dioxide and cellular waste from brain tissue.Blockages that interfere with this blood supply eventually cause thebrain tissue to stop functioning. If the disruption in blood occurs fora sufficient amount of time, the continued lack of nutrients and oxygencauses irreversible cell death (infarction). Accordingly, it isdesirable to provide immediate medical treatment of an ischemic stroke.To access the cerebral vasculature, a physician typically advances acatheter from a remote part of the body (typically a leg) through theabdominal vasculature and into the cerebral region of the vasculature.Once within the cerebral vasculature, the physician deploys a device forretrieval of the obstruction causing the blockage. Concerns aboutdislodged obstructions or the migration of dislodged fragments increasesthe duration of the procedure at time when restoration of blood flow isparamount. Furthermore, a physician might be unaware of one or morefragments that dislodge from the initial obstruction and cause blockageof smaller more distal vessels.

Many physicians currently perform thrombectomies (i.e. clot removal)with stents to resolve ischemic stroke. Typically, the physician deploysa stent into the clot in an attempt to push the clot to the side of thevessel and re-establish blood flow. Tissue plasminogen activator (“tPA”)is often injected into the bloodstream through an intravenous line tobreak down a clot. However, it takes time for the tPA to reach the clotbecause the tPA must travel through the vasculature and only begins tobreak up the clot once it reaches the clot material. tPA is also oftenadministered to supplement the effectiveness of the stent. Yet, ifattempts at clot dissolution are ineffective or incomplete, thephysician can attempt to remove the stent while it is expanded againstor enmeshed within the clot. In doing so, the physician must effectivelydrag the clot through the vasculature, in a proximal direction, into aguide catheter located within vessels in the patient's neck (typicallythe carotid artery). While this procedure has been shown to be effectivein the clinic and is easy for the physician to perform, there remainsome distinct disadvantages to using this approach.

For example, one disadvantage is that the stent may not sufficientlyretain the clot as it pulls the clot to the catheter. In such a case,some or all of the clot might remain the vasculature. Another risk isthat as the stent mobilizes the clot from the original blockage site,the clot might not adhere to the stent as the stent is withdrawn towardthe catheter. This is a particular risk when passing throughbifurcations and tortuous anatomy. Furthermore, blood flow can carry theclot (or fragments of the clot) into a branching vessel at abifurcation. If the clot is successfully brought to the end of the guidecatheter in the carotid artery, yet another risk is that the clot may be“stripped” or “sheared” from the stent as the stent enters the guidecatheter. Regardless, simply dragging an expanded stent (either fully orpartially expanded) can result in undesired trauma to the vessel. Inmost cases, since the stent is oversized compared to the vessel,dragging a fixed metallic (or other) structure can pull the arteriesand/or strip the cellular lining from the vessel, causing further traumasuch as a hemorrhagic stroke (leakage of blood from a cerebral vessel).Also, the stent can become lodged on plaque on the vessel wallsresulting in further vascular damage.

In view of the above, there remains a need for improved devices andmethods that can remove occlusions from body lumens and/or vessels.

SUMMARY

At least some of the embodiments disclosed herein are devices, systems,and methods for retrieving clot material from a blood vessel lumen. Forexample, some embodiments are directed to a retrieval device (such as aclot retrieving device) that includes an elongated shaft configured tobe intravascularly positioned at or adjacent clot material within ablood vessel lumen, and a retrieval assembly coupled to a distal regionof the elongated shaft. The retrieval assembly may include a flexiblecover and a capture structure. The retrieval assembly may be deployedwithin the blood vessel lumen at or near the clot material such that thecapture structure engages or otherwise becomes enmeshed with at least aportion of the clot material, and at least a portion of the coverpresses outward against the blood vessel wall proximal of the capturestructure. Pulling the elongated shaft proximally everts the cover overthe capture structure such that the cover at least partially ensheathesthe capture structure and associated clot material. The retrievalassembly can then be withdrawn to remove the retrieval device andassociated clot material from the patient.

In at least some embodiments of the present technology, a securingelement can be used to secure the cover while the retrieval device is atleast partially resheathed within a delivery sheath and while theretrieval assembly is still in the vasculature. Some embodiments of thesecuring element are attached to the elongated shaft of the retrievaldevice and configured to exert a force against the cover when theretrieval device is pulled proximally to thereby secure the cover.

The subject technology is illustrated, for example, according to variousaspects described below. Various examples of aspects of the subjecttechnology are described as numbered clauses (1, 2, 3, etc.) forconvenience. These are provided as examples and do not limit the subjecttechnology. It is noted that any of the dependent clauses may becombined in any combination, and placed into a respective independentclause, e.g., clause 1, clause 13, or clause 17. The other clauses canbe presented in a similar manner.

-   -   1. A retrieval device deployable through a delivery sheath, the        device comprising: an elongated shaft;    -   a retrieval structure coupled to a distal zone of the elongated        shaft, the retrieval structure including a capture structure and        a cover having (a) a first portion coupled to the distal zone of        the elongated shaft at a location proximal of the capture        structure and (b) a free second portion, wherein, in a delivery        state, the second portion of the cover extends proximally from        the first portion; and    -   a securing element coupled to the elongated shaft proximal to        the first portion of the cover,    -   wherein, when the cover is in the delivery state and at least a        portion of the cover and at least a portion of the securing        element are positioned within the delivery sheath, moving the        retrieval device proximally increases an outward force exerted        by the securing element against at least a portion of the cover        and an inner surface of the delivery sheath, thereby inhibiting        movement of the second portion of the cover relative to the        elongated shaft.    -   2. The retrieval device of clause 1 wherein the cover extends        continuously between the first portion and the second portion,        and wherein the securing element exerts the outward force        against the cover nearer to the second portion than the first        portion.    -   3. The retrieval device of clause 1 wherein:    -   the securing element is in a first state when positioned at        least partially within the delivery sheath and the retrieval        device is moved proximally with respect to the delivery sheath,    -   the securing element is in a second state when positioned at        least partially within the delivery sheath and the retrieval        device is moved distally with respect to the delivery sheath,        and    -   the securing element exerts an outward force against the cover        that is less in the second state than in the first state.    -   4. The retrieval device of clause 1 wherein:    -   the securing element is in a first state when positioned at        least partially within the delivery sheath and the retrieval        device is moved proximally with respect to the delivery sheath,    -   the securing element is in a second state when positioned at        least partially within the delivery sheath and the retrieval        device is moved distally with respect to the delivery sheath,        and    -   the securing element has a cross-sectional area that is greater        in the first state than in the second state.    -   5. The retrieval device of clause 1 wherein the securing element        is a braid or stent coupled to the elongated shaft at a first        connector and a second connector, and wherein the first        connector is proximal to the second connector along the shaft.    -   6. The retrieval device of clause 5 wherein at least one of the        first and second connectors is fixed to the elongated shaft.    -   7. The retrieval device of clause 5 wherein at least one of the        first and second connectors is slidably coupled to the elongated        shaft and the other of the first and second connectors is fixed        to the elongated shaft.    -   8. The retrieval device of clause 5 wherein the securing element        includes a plurality of struts extending from the first        connector to the second connector.    -   9. The retrieval device of clause 1 wherein the securing element        is at least one of a laser cut sphere, a compressible foam or        polymer pad, and a braided structure.    -   10. The retrieval device of clause 1 wherein at least one of the        capture structure and the cover is a mesh.    -   11. The retrieval device of clause 1 wherein the capture        structure is a stent and the cover is a braid.    -   12. The retrieval device of clause 1 wherein, when the retrieval        structure is in the delivery state and the securing element is        outside of the delivery sheath and within a vessel lumen, the        securing element is configured to expand outward against the        cover within the vessel lumen.    -   13. A method of positioning a retrieval device, the method        comprising:    -   advancing at least a portion of a retrieval structure of a        retrieval device distally from a delivery sheath to a partially        deployed state, wherein the retrieval structure is coupled to an        elongated shaft, and wherein (a) during advancement, a securing        element coupled to the elongated shaft is in a first        configuration and a cover of the retrieval structure extends        proximally relative to a capture structure of the retrieval        structure, and (b) in the partially deployed state, at least a        distal portion of the capture structure is distal of the        delivery sheath and at least a portion of the cover remains        within the delivery sheath; and    -   retracting the retrieval device proximally such that the        securing element expands radially to a second configuration        wherein the securing element exerts an outward force against the        cover that is greater than when in the first configuration.    -   14. The method of clause 13 wherein:    -   the cover has a first portion coupled to the elongated shaft, a        free second portion, and extends continuously between the first        portion and second portion, and    -   in the second configuration, the securing element exerts the        outward force against the cover nearer to the second portion        than the first portion and the securing element is configured to        prevent substantial movement of the second portion of the cover        relative to the first portion of the cover.    -   15. The method of clause 13 wherein the securing element has a        cross-sectional area that is greater in the second configuration        than in the first configuration.    -   16. The method of clause 13 wherein the securing element does        not exert a force against the cover in the first configuration.    -   17. A system for retrieving vascular material (such as clot),        the system comprising:    -   a delivery sheath having a distal portion;    -   a retrieval device including an elongated shaft, a retrieval        structure, and a securing element, wherein:        -   the retrieval structure is coupled to a distal zone of the            elongated shaft and includes a capture structure and a            cover,        -   the cover has a first portion coupled to the distal zone of            the elongated shaft and a free second portion,        -   in a partially deployed state, at least a distal portion of            the capture structure extends past the distal portion of the            delivery sheath, at least the second portion of the cover is            within the delivery sheath, and the second portion of the            cover extends proximally from the first portion, and        -   the securing element is coupled to the elongated shaft            proximal to the first portion of the cover, and the securing            element is configured to expand when the device is retracted            proximally from the partially deployed state such that the            securing element grips at least a portion of the cover            between the securing element and an inner surface of the            delivery sheath, thereby preventing substantial movement of            the second portion of the cover relative to the first            portion of the cover while the retrieval device is retracted            proximally.    -   18. The system of clause 17 wherein the capture structure is a        stent and the cover is a braid.    -   19. The system of clause 17 wherein the securing element is        coupled to the elongated shaft at a first connector and a second        connector, wherein the first connector is proximal to the second        connector along the shaft, and wherein the first connector is        slidably coupled to the elongated shaft.    -   20. The system of clause 17 wherein the cover extends        continuously between the first portion and the second portion,        and wherein the securing element grips the cover nearer to the        second portion than the first portion.

Additional features and advantages of the subject technology will be setforth in the description below, and in part will be apparent from thedescription, or may be learned by practice of the subject technology.The advantages of the subject technology will be realized and attainedby the structure particularly pointed out in the written description andclaims hereof as well as the appended drawings.

It is to be understood that both the foregoing general description andthe following detailed description are explanatory and are intended toprovide examples and further explanation of the subject technology asclaimed.

BRIEF DESCRIPTION OF THE DRAWINGS

Many aspects of the present technology can be better understood withreference to the following drawings. The components in the drawings arenot necessarily to scale. Instead, emphasis is placed on illustratingclearly the principles of the present disclosure.

FIG. 1A is a side view of a distal portion of a clot retrieval deviceshown with a retrieval assembly in a first configuration in accordancewith the present technology.

FIG. 1B is a side view of the distal portion of the clot retrievaldevice of FIG. 1A, shown with the retrieval assembly shown in a second,everted configuration.

FIGS. 2A-2G illustrate a method of removing clot material from a bloodvessel lumen using the clot retrieval device shown in FIGS. 1A and 1B.

FIG. 3A is a cross-sectional side view of the retrieval device in FIG.1A being advanced distally through a delivery sheath.

FIGS. 3B-3D are enlarged cross-sectional side views of a proximalportion of the retrieval device in FIG. 3A showing a securing element ina stationary state, a first state, and a second state, respectively.

FIG. 4A is a cross-sectional side view of the retrieval device in FIG.1A, being held stationary, and in a partially deployed position from adelivery sheath.

FIG. 4B is a cross-sectional side view of the retrieval device in FIG.1A, being retracted proximally, and in a partially deployed positionfrom the delivery sheath.

DETAILED DESCRIPTION

The present technology provides devices, systems, and methods forsecuring a flexible interventional device against an inner wall of adelivery sheath to assist in resheathing the device while positioningthe device in a blood vessel lumen. Although many of the embodiments aredescribed below with respect to devices, systems, and methods forremoving clot material from a blood vessel lumen or otherwise treating acerebral embolism, other applications and other embodiments in additionto those described herein are within the scope of the technology. Forexample, the securing devices of the present technology may be used tosecure any flexible interventional device (e.g., a mesh, a braid, afabric, etc.) configured to be intravascularly delivered to a body lumenthrough a delivery sheath.

FIGS. 1A and 1B are side views of a distal portion of some embodimentsof a retrieval device 10 (“device 10”) outside of a blood vessel in anexpanded, relaxed (e.g., unconstrained) configuration in accordance withthe present technology. The retrieval device 10 is shown in first andsecond configurations in FIGS. 1A and 1B, respectively. As shown inFIGS. 1A and 1B, the retrieval device 10 includes an elongated shaft 12(“shaft 12”) and a retrieval assembly 14 coupled to a distal region ofthe elongated shaft 12 via a connection assembly 120. The retrievalassembly 14 is configured to be intravascularly positioned at oradjacent clot material (or other material to be retrieved such asplaques, foreign bodies, etc.) within a blood vessel lumen and includesa capture structure 100 and a flexible cover 200. In some embodiments,the capture structure 100 and the cover 200 are fixed to the elongatedshaft 12 at generally the same location, or the capture structure 100and cover 200 may be coupled to the shaft 12 at different locationsand/or may be slidable with respect to the elongated shaft 12.

The capture structure 100 has a low-profile configuration (not shown)when constrained within a delivery catheter (e.g., a microcatheter) andan expanded configuration for securing and/or engaging clot material orother obstructions within a blood vessel lumen (e.g., a cerebral bloodvessel lumen) and/or for restoring blood flow within the blood vessel.The capture structure 100 has a proximal portion 100 a coupled to theshaft 12 and a distal portion 100 b. The capture structure 100 furtherincludes an open cell framework or body 108 (FIG. 1A) and a couplingregion 102 (FIG. 1A) extending proximally from the body 108. In someembodiments, for example as shown in FIGS. 1A and 1B, a distal portion100 b of the capture structure 100 can be generally tubular (e.g.,cylindrical), and the proximal portion 100 a of the capture structure100 tapers proximally to the coupling region 102. In some embodiments,the distal terminus of the distal portion 100 b coincides with a distalterminus 101 of the capture structure 100 and/or retrieval assembly 14.

Referring again to FIGS. 1A and 1B, in some embodiments the capturestructure 100 is a mesh structure formed of a superelastic material(e.g., Nitinol or other resilient or self-expanding material) configuredto self-expand when released from the delivery catheter. For example, insome embodiments the capture structure 100 may be a stent and/orstentriever, such as Medtronic's Solitaire™ Revascularization Device,Stryker Neurovascular's Trevo® ProVue™ Stentriever, or other suitabledevices. In other embodiments, the capture structure 100 may include aplurality of braided filaments. Examples of suitable capture structures100 include any of those disclosed in U.S. Pat. No. 7,300,458, filedNov. 5, 2007, U.S. Pat. No. 8,940,003, filed Nov. 22, 2010, U.S. Pat.No. 9,039,749, filed Oct. 1, 2010, and U.S. Pat. No. 8,066,757, filedDec. 28, 2010, each of which is incorporated by reference herein in itsentirety.

The cover 200 includes a first end portion 200 a coupled to the shaft 12via the connection assembly 120, a free second end portion 200 b, and acover wall 200 c extending between the first end portion 200 a and thesecond end portion 200 b. As used herein to describe the second endportion 200 b of the cover 200, the term “free” refers to a portion ofthe cover 200 that is not fixed to the elongated shaft 12 and may moveradially and/or longitudinally with respect to the shaft 12. The cover200 is flexible such that it is movable between a first position (FIG.1A) in which the free second end portion 200 b is proximal of the firstend portion 200 a and a second position (FIG. 1B) in which the cover 200is inverted over the capture structure 100 such that a distal terminus201 (FIG. 1B) of the cover 200 is at or distal to the distal terminus101 of the capture structure 100 and/or to the first end portion 200 a.As shown in FIG. 1A, when the cover 200 is in the first position in anexpanded, relaxed state, some embodiments of the cover 200 may have aleading edge 204 that overlaps the coupling region 102 of the capturestructure 100 but does not extend beyond the coupling region 102 tooverlap the body 108 of the capture structure 100. In some embodiments,the leading edge 204 of the cover 200 may also overlap all or a portionof the length of the body 108 when the cover 200 is in the firstposition. As shown in FIG. 1B, when the cover 200 is in the secondposition, the free second end portion 200 b is distal of the first endportion 200 a and distal of the distal terminus 101 of the capturestructure 100. As such, when in the second position, the cover wall 200c surrounds the capture structure 100.

The cover 200 can comprise a mesh and/or braid of a plurality of wires(e.g., filaments, threads, sutures, fibers or the like) that have beeninterwoven to form a structure having openings (e.g., a porous fabric).The mesh and/or braid can be composed of metals, polymers, composites,and/or biologic materials. Polymer materials can include Dacron,polyester, polypropylene, nylon, Teflon, polytetrafluoroethylene (PTFE),tetrafluoroethylene, polyethylene terephthalate, polyactic acid (PLA)silicone, polyurethane, polyethylene, polycarbonate, styrene, polyimide,PEBAX, Hytrel, polyvinyl chloride, high-density polyethylene,low-density polyethylene, polyether ether ketone (PEEK), rubber, latex,and/or other suitable polymers known in the art. Other materials knownin the art of elastic implants can also be used. Metal materials caninclude, but are not limited to, nickel-titanium alloys (e.g. Nitinol),platinum, cobalt-chromium alloys, stainless steel, tungsten or titanium.In certain embodiments, metal filaments may be highly polished and/orsurface treated to further improve their hemocompatibility. The cover200 can be constructed solely from metallic materials without theinclusion of any polymer materials, solely from polymer materialswithout the inclusion of any metallic materials, or a combination ofpolymer and metallic materials.

In some embodiments, some or all of the wires of the cover 200 aredrawn-filled tube (“DFT”) wires having a radiopaque core (e.g.,platinum, tantalum, gold, tungsten, etc.) surrounded by a superelasticmaterial (e.g., Nitinol, a cobalt-chromium alloy, etc.). The radiopaquecore may comprise about 5% to about 50% (e.g., 10%, 15%, 20%, 25%, 30%,35%, 40%, 45%) of the total-cross-sectional area of the individualwires. In some embodiments, the cover 200 may have 72-144 total wires(e.g., 72, 96 128, 144, etc.) Moreover, some or all of the wires mayhave a wire diameter of about 0.005 inches to about 0.015 inches (e.g.,0.008 inches, 0.01 inches, etc.). In some embodiments, all of the wireshave the same diameter, and in other embodiments some of the wires havedifferent diameters.

FIGS. 2A-2G illustrate a method of removing clot material from the lumenof a blood vessel V using the retrieval device 10 of the presenttechnology. The retrieval device 10 shown in FIGS. 2A-2G does notinclude the securing element 330, which is described in detail belowwith reference to FIGS. 3A-4B. As shown in FIG. 2A, a guidewire 1 may beadvanced through the clot material CM such that a distal terminus of theguidewire 1 is distal of the clot material CM. Next, a delivery catheter2 may be delivered over the guidewire 1 so that a distal portion of thedelivery catheter 2 is positioned at or near the clot material CM. Asshown in FIG. 2B, in some embodiments the delivery catheter 2 may beadvanced over the guidewire 1 through the clot material CM such that adistal terminus of the delivery catheter 2 is distal of the clotmaterial CM. With the delivery catheter 2 in position, the guidewire 1may be withdrawn. The retrieval device 10 may then be advanced throughthe delivery catheter 2 in a low-profile configuration until a distalterminus 101 of the capture structure 100 (shown schematically in FIG.2B) is at or adjacent the distal terminus of the delivery catheter 2. Asshown in FIGS. 2C and 2D, the delivery catheter 2 may then be pulledproximally relative to the retrieval device 10 to release the capturestructure 100, thereby allowing the capture structure 100 to self-expandwithin the clot material CM. As the capture structure 100 expands, thecapture structure 100 engages and/or secures the surrounding clotmaterial CM, and in some embodiments may restore or improve blood flowthrough the clot material CM. In some embodiments, the capture structure100 may be expanded distal of the clot material CM such that no portionof the capture structure 100 is engaging the clot material CM while thecapture structure 100 is in the process of expanding toward the vesselwall. In some embodiments, the capture structure 100 is configured toexpand into contact with the blood vessel wall, or the capture structure100 may expand to a diameter that is less than that of the blood vessellumen such that the capture structure 100 does not engage the entirecircumference of the blood vessel wall.

As shown in FIG. 2D, the delivery catheter 2 may continue advancingproximally (as the user continues pulling it proximally) to release thecover 200 such that at least a portion of the cover wall 200 c expandsinto contact with the blood vessel wall when the cover 200 is in thefirst position. Once the delivery catheter 2 is moved proximal of thecover 200 in the first position and both the cover 200 and the capturestructure 100 are expanded within the vessel lumen, the retrievalassembly 14 is in the first configuration.

As shown in FIG. 2E, when the elongated shaft 12 is pulled proximallywhile the retrieval assembly 14 is in the first configuration, frictionbetween the blood vessel wall and the cover wall 200 c prevents orresists proximal movement of the free second end portion 200 b of thecover 200 while the first end portion 200 a of the cover 200 moves in aproximal direction with the capture structure 100. In other words,expansion of the cover 200 provides sufficient friction against thewalls of the vessel V to overcome the column strength of the cover wall200 c, thereby causing the cover wall 200 c to remain in place and/ormove less than the first end portion 200 a of the cover 200 so that thecover wall 200 c inverts over the proximally advancing capture structure100 and any associated clot material CM. As the elongated shaft 12 ismoved proximally and the cover 200 is inverting, the capture structure100 moves proximally relative to the leading edge 204 of the cover 200so that the length of the capture structure 100 coextensive with thecover 200 increases. Eventually, the cover 200 completely inverts fromthe first position over the capture structure 100, thereby furthersecuring any clot material held by or within the capture structure. Asshown in FIG. 2G, the retrieval device 10 may continue advancingproximally (as the user continues pulling it proximally) until theretrieval assembly 14 is positioned within the delivery catheter 2. Thedelivery catheter 2, device 10, and associated clot material CM may thenbe withdrawn from the patient.

In some instances, the physician may desire to move the retrievalassembly 14 proximally relative to the delivery catheter 2 while atleast a portion of the retrieval assembly 14 is still within thedelivery catheter 2. For example, in some instances it may be desirableto pull at least a portion of the retrieval assembly 14 back into thedelivery catheter 2 mid-deployment so that the retrieval assembly 14 canbe repositioned and redeployed. More specifically, the physician mightadvance the capture structure 100 and part of the cover 200 outside ofthe delivery catheter 2 before determining that the retrieval assembly14 is not at a desired location within a blood vessel. In otherinstances, it may be desirable to retract the retrieval assembly 14proximally when it has yet to be deployed and is still fully within thedelivery catheter 2. As used herein, the term “resheath” encompasses anyproximal movement of the retrieval assembly 14 within the deliverycatheter 2, whether or not the retrieval assembly 14 has been partiallydeployed from (i.e., advanced outside of) the delivery catheter 2.

While the free second end portion 200 b of the cover 200 allows thecover 200 to invert over the capture structure 100, it can hinderefforts to resheath the retrieval assembly 14 within the deliverycatheter 2. Specifically, when the retrieval assembly 14 is retractedproximally with no means of securing the cover 200, friction between thedelivery catheter 2 and the cover wall 200 c can prevent or resistproximal movement of the free second end portion 200 b of the cover 200while the first end portion 200 a of the cover 200 moves in a proximaldirection with the shaft 12 (e.g., in a similar manner to the intendedmovement of the cover 200 within a vessel lumen). This can cause thecover 200 to bunch up within the delivery catheter 2 and/or snag on thecapture structure 100. As a result, the physician might have to fullyremove the retrieval assembly 14 from the delivery catheter 2 (e.g.,through a larger outer catheter) in order to prepare the retrievalassembly 14 for redeployment. As described in further detail below withreference to FIGS. 3A-4B, a securing element 330 can be configured tosecure the cover 200 while the retrieval assembly 14 is resheathed,thereby making it possible, and/or reducing the time required, toredeploy the retrieval assembly 14.

FIG. 3A is a cross-sectional side view showing the retrieval assembly 14constrained within a delivery sheath 415. The cover 200 is in the firstposition (i.e., the free second end portion 200 b is proximal of thefirst end portion 200 a) and positioned between the securing element 330and an interior surface 417 of the delivery sheath 415. The securingelement 330 is coupled to the shaft 12 via the first connector 332 andthe second connector 334 (collectively “connectors 332, 334”). In someembodiments, the first connector 332 is fixed to the shaft 12 and thesecond connector 334 is slidably coupled to the shaft 12. Accordingly,when the shaft 12 moves proximally, the shaft 12 can slide proximally bysome distance through the second connector 334 such that the firstconnector 332 moves toward the second connector 334. Likewise, when theshaft 12 moves distally, the shaft 12 can slide distally by somedistance through the second connector 334 such that the first connector332 moves apart from the second connector 334. Changes in the positionof the second connector 334 relative to the first connector 332 cancorrespondingly change characteristics of the securing element 330—suchas its shape, cross-sectional dimension (e.g., radius), etc. In someembodiments, the securing element 330 is fixedly coupled to the shaft 12at the second connector 334 and slidably coupled to the shaft 12 at thefirst connector 332, or the securing element 330 is fixedly coupled orslidably coupled at both connectors 332, 334.

As shown in FIG. 3A, the securing element 330 can radially expand withinthe delivery sheath 415 such that the securing element 330 contacts thecover 200 and exerts an outward force against both the cover 200 and theinterior surface 417 of the delivery sheath 415. In some embodiments,the securing element 330 is radially biased such that it expands outwardand contacts the cover 200 while the shaft 12 is advanced distally,retracted proximally, and held stationary. In some embodiments, thesecuring element 330 only expands outward and contacts the cover 200when the elongated shaft 320 is retracted proximally. This may be done,for example, by configuring the first connector 332 as a fixed connectorand the second connector 334 as a moveable connector.

The securing element 330 can be a braid or stent, a laser cut expandablecomponent such as a sphere, a compressible foam rubber or polymer pad(in either case in suitable shape such as a cylinder, sleeve or sphere),or one or more struts extending between the first connector 332 and thesecond connector 334. In one embodiment, the securing element 330 is aheat-set array of nitinol wires. The size of the wires and the shape andconfiguration of the array can be chosen to give the securing element330 different characteristics. For example, in some embodiments, usingthicker wires or increasing the number of wires in the array canincrease a frictional force between the securing element 330 and thecover 200. The securing element 330 can further have any suitable shapeor relative size. For example, the securing element 330 can have agenerally spherical shape or an outer surface with a different generallycurved or angular shape.

FIGS. 3B-3D are enlarged cross-sectional side views of the securingelement 330 in a stationary state, a first state, and a second state,respectively. FIG. 3B shows the securing element 330 in the stationarystate in which no force is applied to the shaft 12 (i.e., the shaft 12is neither being advanced distally nor retracted proximally). As shown,the securing element 330 expands radially outward and contacts the cover200. In other embodiments, the securing element 330 is configured to notcontact the cover 200 in the stationary state. For example, the securingelement 330 can be compressed against the shaft 12 or, in anunconstrained state, only expand radially outward to a smaller diameterthan the cover 200 in the stationary state within the delivery sheath415. A distance D_(s) between the connectors 332, 334 along the shaft 12depends on the extent of expansion of the securing element 330 and therelative dimensions of the securing element 330 and the delivery sheath415, among other factors. The securing element 330 can further have across-sectional dimension (e.g., area) defined along the plane R_(s)that depends on the distance D_(s) and the dimensions of the deliverysheath 415.

FIG. 3C illustrates the securing element 330 in the first state when theshaft 12 is advanced distally in the direction of force F₁. Advancingthe shaft 12 distally pushes the first connector 332 distally and causesthe shaft 12 to slide distally through the second connector 334 suchthat a distance D₁ between the connectors 332, 334 increases relative towhen the securing element 330 is in the stationary state (FIG. 3B). Asthe distance D₁ increases, the securing element 330 contracts radiallyand a cross-sectional dimension (e.g., area) of the securing element 330defined along the plane R₁ correspondingly decreases. The distance D₁depends on the magnitude of the force F₁ applied to the shaft 12 in thedistal direction, the radial bias of the securing element 330, and therelative dimensions of the securing element 330 and the delivery sheath415, among other factors. As illustrated in FIG. 3C, the securingelement 330 can have an outer surface that has a generally angular shapein the first state.

In the embodiment shown in FIG. 3C, the securing element 330 can exert amoderate outward force against the cover 200 and an interior surface 417of the delivery sheath 415 in the first state. The outward force exertedagainst the cover 200 in the first state is not enough to hinder distaladvancement of retrieval assembly 14. That is, the retrieval assembly 14can be advanced through the delivery sheath 415 despite the frictionbetween the cover 200 and the interior surface 417 of the deliverysheath 415 caused by the securing element 330 in the first state. Inother embodiments, the securing element 330 is configured not to exertan outward force against the cover 200 while the shaft 12 is advanceddistally. For example, the securing element 330 can compress down to theshaft 12 such that it does not contact the cover 200 in the first state.

FIG. 3D illustrates the securing element 330 in the second state whenthe shaft 12 is retracted proximally in the direction of forceF₂Proximal movement of the shaft 12 pulls the first connector 332proximally and causes the shaft 12 to slide proximally through thesecond connector 334 such that a distance D₂ between the connectors 332,334 along the shaft 12 is less than the distance D₁ in the first state(FIG. 3C) and the distance D_(s) in the stationary state (FIG. 3B). Asthe securing element 330 foreshortens (i.e., the distance D₂ decreases),the securing element 330 expands radially outward such that across-sectional dimension (e.g., diameter) of the securing element 330defined along the plane R₂ correspondingly increases. The distance D₂depends on the magnitude of the force F₂ applied to the shaft 12 in theproximal direction, the radial bias of the securing element 330, and therelative dimensions of the securing element 330 and the delivery sheath415, among other factors.

In the second state, the securing element 330 contacts and pushesoutwardly against the cover 200 at a contact region 425 of the cover200. The contact region 425 can have a greater or smaller area dependingon the configuration of the securing element 330 and the amount of forceF₂ applied to the shaft 12. For example, in some embodiments, as thedistance D₂ between the connectors 332, 334 decreases (e.g., the ForceF₂ is increased), the contact region 425 becomes larger as the securingelement 330 expands radially. The securing element 330 exerts a forceagainst the cover 200 at the contact region 425, and indirectly exerts aforce against the interior surface 417 of the delivery sheath 415 (i.e.,through the cover 200). The force exerted by the securing element 330 onthe cover 200 can be greater in the second state than in the stationarystate (FIG. 3B) and the first state (FIG. 3C).

In operation, the securing element 330 secures (e.g., grips) the cover200 in the second state. For example, the securing element 330 isconfigured such that there is more friction between the securing element330 and an inner surface 421 of the cover 200 than between an outersurface 423 of the cover 200 and the interior surface 417 of thedelivery sheath 415 in the second state. More specifically, frictionbetween the securing element 330 and the contact region 425 of the cover200 causes a frictional force that opposes relative motion between thesecuring element 330 and the cover 200. Therefore, the cover 200 canslide proximally relative to the delivery sheath 415—but not relative tothe securing element 330—when the force F₂ is applied to the shaft 12.

The forces acting on the cover 200 can be more complicated thanpresently described. For example, the physical structure of the cover200 can introduce a column force when the retrieval assembly 14 isretracted proximally. Moreover, the securing element 330 can impart somehorizontal forces on the cover 200 at boundary regions between thecontact region 425 and non-contacted portions of the cover 200.

In the embodiment illustrated in FIG. 3D, the contact region 425 isnearer to the free second end portion 200 b of the cover 200 than thefirst end portion 200 a of the cover 200. In certain embodiments, aproximal region 427 of the cover 200 is proximal of the contact region425. In operation, the proximal region 427 is not secured by thesecuring element 330 as described above. That is, friction between theproximal region 427 and the delivery sheath 415 can prevent or resistproximal movement of the proximal region 427 of the cover 200 (which thesecuring element 330 is configured to overcome for the rest of the cover200). This can result in some bunching of the proximal region 427 of thecover 200 when the retrieval assembly 14 is retracted proximally.However, by configuring the proximal region 427 to be small compared tothe overall size of the cover 200, the effect can be made to beinsubstantial. Accordingly, the retrieval assembly 14 can still beresheathed within the delivery sheath 415 without requiring thephysician to fully remove the retrieval assembly 14 to ready it forredeployment.

In some embodiments, the cover 200 does not include any proximal region427 when the securing element 330 is in the second state. For example,the securing element 330 can be positioned such that the contact region425 is at or immediately adjacent to a terminus 429 (i.e., absolute end)of the cover 200. In particular, the second connector 334 can be coupledto the shaft 12 at a position that is proximal of the terminus 429 ofthe cover 200. Accordingly, the terminus 429 can be between theconnectors 332, 334 such that, in the second state, the contact region425 of the cover 200 includes the terminus 429 of the cover 200. In suchembodiments, even minor bunching or other undesired movement of thecover 200 can be avoided as the retrieval assembly 14 is retractedproximally.

In order for the securing element 330 to secure the cover 200 asdescribed above, at least a portion of the cover 200 and a portion ofthe securing element 330 must remain within the delivery sheath 415. Inparticular, at least portion of the contact region 425 of the cover 200must be within the delivery sheath 415 to enable resheathing of theretrieval assembly 14. In some embodiments, the securing element 330 isconfigured to expand outward against the cover 200 when the securingelement 330 is fully outside of the delivery sheath 415 and within avessel lumen. In some such embodiments, the securing element 330 helpsexpand the cover 200 within the vessel lumen to facilitate moving thecover 200 to the second position (FIG. 1B).

FIGS. 4A and 4B illustrate various stages of a method for resheathingthe retrieval assembly 14 including the securing element 330 inaccordance with embodiments of the present technology. In operation, thedelivery sheath 415 with the retrieval assembly 14 positioned therein(as shown in FIG. 3A) can be positioned at a treatment site. As shown inFIG. 4A, the retrieval assembly 14 can then be advanced to a partiallydeployed position. In the partially deployed position: (i) at least aportion of the cover 200 remains within the delivery sheath 415, and(ii) at least a portion of the securing element 330 remains within thedelivery sheath 415. In some embodiments, at least the distal terminus101 of the capture structure 100 is distal of the of the delivery sheath415 (e.g., extends past a distal terminus 516 of the delivery sheath415) in the partially deployed position. As shown in FIG. 4B, thecapture structure 100 is fully outside of the delivery sheath 415, aportion of the cover 200 is within the delivery sheath 415, and thesecuring element 330 is fully within the delivery sheath 415.

FIG. 4A shows the securing element 330 in the stationary state. As theretrieval assembly 14 is advanced to the partially deployed positionshown in FIG. 4A, the securing element 330 can be in the first state.However, before fully deploying the retrieval assembly 14, the physicianfirst assesses whether the retrieval assembly 14 is located at a desiredlocation within the vasculature (e.g., at the site of clot material tobe removed). When distal advancement is stopped, the securing element330 can be in the stationary state as illustrated in FIG. 4A. If thephysician determines that the retrieval assembly 14 is in the desiredlocation, the physician can then advance the retrieval assembly 14 to adeployed state (e.g., where the cover 200 and capture structure 100 arefully outside the delivery sheath 415). However, if the physiciandetermines that the there is a more desirable location, the physiciancan resheath the retrieval assembly 14 within the delivery sheath 415 sothat the retrieval assembly 14 can be moved to, and later deployed at,another location.

FIG. 4B shows the retrieval assembly 14 in another partially deployedstate and being retracted (to the right of the page) to a position moreproximal within the delivery sheath 415. In the partially deployed stateshown in FIG. 4B: (i) the distal terminus 101 of the capture structure100 is outside the delivery sheath 415, (ii) a portion of the capturestructure 100 is within the delivery sheath 415, and (iii) the cover 200is fully within the delivery sheath 415. A physician may retract theretrieval assembly 14 by pulling proximally on the shaft 12, or byotherwise applying a proximal force to the shaft 12. During retraction,the securing element 330 grips the cover 200 in the second state toprevent substantial movement of the cover 200 relative to the shaft 12.Therefore, the retrieval assembly 14 can be resheathed withoutsignificant bunching of the cover 200 that would otherwise impede theresheathing process. In some embodiments, the retrieval assembly 14 isretracted proximally until it is fully within the delivery sheath 415(as shown in FIG. 3A). In other embodiments, only a portion of theretrieval assembly 14 is retracted to a more proximal position withinthe delivery sheath 415 (e.g., from the partially deployed positionshown in FIG. 4A to the partially deployed position shown in FIG. 4B).

Once resheathed, the delivery sheath 415 can be moved to reposition theretrieval assembly 14 at another location within the vasculature. Someembodiments of the present technology accordingly can allow thephysician to partially deploy and then resheath the retrieval assembly14 as many times as necessary.

This disclosure is not intended to be exhaustive or to limit the presenttechnology to the precise forms disclosed herein. Although specificembodiments are disclosed herein for illustrative purposes, variousequivalent modifications are possible without deviating from the presenttechnology, as those of ordinary skill in the relevant art willrecognize. In some cases, well-known structures and functions have notbeen shown and/or described in detail to avoid unnecessarily obscuringthe description of the embodiments of the present technology. Althoughsteps of methods may be presented herein in a particular order, inalternative embodiments the steps may have another suitable order.Similarly, certain aspects of the present technology disclosed in thecontext of particular embodiments can be combined or eliminated in otherembodiments. Furthermore, while advantages associated with certainembodiments may have been disclosed in the context of those embodiments,other embodiments can also exhibit such advantages, and not allembodiments need necessarily exhibit such advantages or other advantagesdisclosed herein to fall within the scope of the present technology.Accordingly, this disclosure and associated technology can encompassother embodiments not expressly shown and/or described herein.

Throughout this disclosure, the singular terms “a,” “an,” and “the”include plural referents unless the context clearly indicates otherwise.Similarly, unless the word “or” is expressly limited to mean only asingle item exclusive from the other items in reference to a list of twoor more items, then the use of “or” in such a list is to be interpretedas including (a) any single item in the list, (b) all of the items inthe list, or (c) any combination of the items in the list. Additionally,the terms “comprising” and the like are used throughout this disclosureto mean including at least the recited feature(s) such that any greaternumber of the same feature(s) and/or one or more additional types offeatures are not precluded. Reference herein to “one embodiment,” “anembodiment,” or similar formulations means that a particular feature,structure, operation, or characteristic described in connection with theembodiment can be included in at least one embodiment of the presenttechnology. Thus, the appearances of such phrases or formulations hereinare not necessarily all referring to the same embodiment. Furthermore,various particular features, structures, operations, or characteristicsmay be combined in any suitable manner in one or more embodiments.

We claim:
 1. A method of positioning a retrieval device, the methodcomprising: advancing at least a portion of a retrieval structure of aretrieval device distally from a delivery sheath to a partially deployedstate, wherein the retrieval structure is coupled to an elongated shaft,and wherein (a) during advancement, a securing element coupled to theelongated shaft is in a first configuration and a cover of the retrievalstructure extends proximally relative to a capture structure of theretrieval structure, and (b) in the partially deployed state, at least adistal portion of the capture structure is distal of the delivery sheathand at least a portion of the cover remains within the delivery sheath;and retracting the retrieval device proximally such that the securingelement expands radially to a second configuration wherein the securingelement exerts an outward force against the cover that is greater thanwhen in the first configuration.
 2. The method of claim 1 wherein: thecover has a first portion coupled to the elongated shaft, a free secondportion, and extends continuously between the first portion and secondportion, and in the second configuration, the securing element exertsthe outward force against the cover nearer to the second portion thanthe first portion and the securing element is configured to preventsubstantial movement of the second portion of the cover relative to thefirst portion of the cover.
 3. The method of claim 1 wherein thesecuring element has a cross-sectional area that is greater in thesecond configuration than in the first configuration.
 4. The method ofclaim 1 wherein the securing element does not exert a force against thecover in the first configuration.
 5. The method of claim 1 whereinretracting the retrieval device proximally comprises retracting theelongated shaft proximally.
 6. The method of claim 1 wherein retractingthe retrieval device proximally comprises retracting the capturestructure proximally.
 7. The method of claim 1 wherein retracting theretrieval device increases a cross-sectional area of the securingelement.
 8. The method of claim 1 wherein retracting the retrievaldevice causes the securing element to have more contact with the cover.9. The method of claim 1 wherein the securing element has a longitudinaldimension that is greater in the first configuration than in the secondconfiguration.
 10. A method of positioning a retrieval device, themethod comprising: providing a retrieval structure coupled to anelongated shaft, the retrieval structure including a flexible cover andan expandable securing element; advancing at least a portion of theretrieval structure distally from a delivery sheath such that at least aportion of the cover remains within the delivery sheath; and retractingthe elongated shaft such that the securing element expands radiallyagainst the cover, thereby inhibiting relative motion between thesecuring element and the cover.
 11. The method of claim 10, whereinretracting the elongated shaft causes the securing element to expandfrom a first configuration to a second configuration, wherein, when inthe second configuration, the securing element exerts an outward forceagainst the cover that is greater than when in the first configuration.12. The method of claim 11 wherein the securing element has across-sectional area that is greater in the second configuration than inthe first configuration.
 13. The method of claim 11 wherein the securingelement has a longitudinal dimension that is greater in the firstconfiguration than in the second configuration.
 14. The method of claim11 wherein the securing element does not exert a force against the coverin the first configuration.
 15. The method of claim 11 wherein, when inthe second configuration, the cover can slide proximally relative to thedelivery sheath.
 16. The method of claim 10 wherein the retrievalstructure further comprises a capture structure, and wherein duringadvancement, (i) the cover extends proximally relative to the capturestructure, and (ii) at least a distal portion of the capture structureis distal of the delivery sheath.
 17. The method of claim 10 wherein thesecuring element further comprises a first connector fixed to theelongated shaft, and a second connector spaced apart from the firstconnector and slidably coupled to the elongated shaft, whereinretracting the elongated shaft causes the first connector to approachthe second connector.
 18. The method of claim 10, wherein the securingelement comprises a braid or stent.